Liquid cooled microwave switch



Dec. 6, 1966 w. H. WRIGHT, JR 3,290,620

LIQUID COOLED MICROWAVE SWITCH Filed Sept. 5, 1963 FlC.

COOLANT GIRCULATOR I INVENTOR,

WILLIAM H. WRIGHT JR BY 7% mjzfmg M 32% 1 I M CHM/ 6. ATTORNEYS United States Patent Ofifice 3,290,629 Patented Dec. 6, 1966 3,290,620 LIQUID COOLED MICROWAVE SWITCH William H. Wright, Jr., Neptune, N.J., assignor to the United States of America as represented by the Secretary of the Army Filed Sept. 3, 1963, Ser. No. 306,398 9 Claims. (Cl. 33313) The invention described herein may be manufactured and used by or for the Governmentfor governmental purposes, without the payment of any royalty thereon.

This invention relates to microwave switching components for controlling high power microwave energy and particularly to means for effectively removing excessive heat developed during operation of such devices thereby protecting the duplexer from heat damage.

The factor limiting the power handling capacity of such devices revolves chiefly about the failure temperature of the dielectric material used to form the discharge chamber of the duplexer. As the power in the system in which the duplexer is installed is increased a corresponding demand for greater cooling facility arises until a point is reached beyond which conventional cooling means becomes ineffective. Thus the capacity of the duplexer is greatly limited.

In prior devices it has been found diflicult to produce a duplexer having adequate heat dissipating capacity. One reason for this condition is the inability in known devices to sufficiently reduce the path length of heat transfer from the most intense discharge point to the surrounding metal parts. In the present invention reduction in path length has been accomplished and the efficiency of heat exchange has been optimized. As a result the power handling capacity of the device has been greatly increased.

Briefly the invention may be described as follows. The duplexing device of the invention is of the type having a resonant iris and a gas filled chamber coupled to the microwave energy to be controlled. The iris is formed in a solid block of electrically and thermally conductive metal and opens into a transverse cylindrical bore in which is received a cylindrical dielectric discharge chamber which fits snugly into the bore and is registered with the iris. High power energy entering thru the iris causes ionization of the ionizable gas in the chamber. In addition a tube of copper or other good thermally and electrically conductive material extends axially thru the cavity and is sealed into the walls thereof. The tube extends beyond the waveguide and is connected to a cooling liquid circulating means. The coolant may be water or any suitable liquid chosen without regard for its dielectric properties. As will be pointed out hereinafter this device presents optimum heat eliminating capability.

It is a primary object of this invention to provide a duplexing device having a construction which provides maximum heat exchange rate between the source of the heat and the outer readily cooled portions of the device.

A further object of the invention is to provide a duplexing device having increased power handling capacity without over heating.

A further object of the invention is to provide a duplexing unit wherein the effective thermal paths extending from the area of creation of maximum temperature to the outer readily cooled portions of the system are shortened.

A further object of the invention is to provide a heat removing element disposed at the point of maximum temperature and therefore having maximum heat exchange capability.

A further object of the invention is to provide an efiicient duplexing element wherein a minimum volume of dielectric is used in the discharge chamber thereby minimizing insertion loss and heat dissipated in the dielectric.

A still further object of the invention is to provide a duplexer construction wherein the coolant fluid is electrically isolated from the microwave energy. Therefore the coolant may be chosen for cooling efficiency, and for ready availability in large quantities at low expense without compromise in respect to desirable electrical properties.

A further object of the invention is to provide a duplexing unit wherein there is a large area of contact between the dielectric discharge envelope and metallic surrounding elements which may readily be cooled.

A further object of the invention is to provide, in a duplexer of the type indicated, means for readily replacing the dielectric discharge envelope.

Other objects and features of the invention will more fully appear from the following detailed description and will be particularly pointed out in the claims.

To provide a better understanding of the invention a particular embodiment thereof will be described and illustrated in the accompanying drawing wherein:

FIG. 1 is a cross section on line 1-1 FIG. 3.

FIG. 2 is an end elevation of the apparatus showing the tuned iris window thereof.

FIG. 3 is a cross section on line 3-3 FIG. 2 showing the manner of incorporating the device in a waveguide system.

The invention achieves an optimum result in the rapid removal of excess heat generated within the discharge chamber and thus protects the dielectric material out of which the chamber is made. The particular embodiment of the invention described herein is suitable for use as a pre-TR unit for protecting the receiver in a radar system. The device may however be used in any application where high speed switching of microwave energy is required.

As shown in FIG. 3 the duplexer 10 is inserted in a waveguide 11 extending transversely from a main waveguide 12 and communicating with the receiver of a radar system. The waveguide 12 carries the operating power for the system and extends from a source of microwave energy such as a magnetron to the antenna of a radar or other load device.

The duplexer is of the type having a resonant iris and a discharge chamber coacting therewith to produce the desired shorting action within its waveguide when exposed to high energy power. The discharge chamber 13 is desirably cylindrical in form and is made of quartz or other dielectric material capable of withstanding high temperatures. In the prior art double wall cylinders have been used having ionizing gas between the walls. In the present invention the chamber is a single thin wall vessel enclosing an ionizable gas such as argon or the like. The single wall provides for rapid heat exchange from inside to the metal surfaces outside of the chamber.

The member 13 is received in a bore 14 extending thru a block 15 of material which is a good heat conductor such as aluminum. Desirably the block is flat having parallel side faces and is slightly thicker than the diameter of the chamber 13 but may be of any suitable conformation. The block is mounted in the waveguide by clamping it between the flanges 16 of the waveguide 11 by a plurality of bolts 17. The bore 14 extends transversely thru the block in the central plane of the Waveguide between the two wide walls thereof.

Communicating with the bore 14 are a pair of resonant irises 18 formed in the block situated horizontally upon the said central plane and proportioned in accordance with the operating frequency of the system. It will thus be seen that high power energy in the main waveguide will ionize the gas in the chamber and create a short circuit in the waveguide 11 thus closing the guide 11 to flow of energy to the radar receiver during transmission of a pulse.

The block 15 may be extended above and below the outer walls of the waveguide 11 to provide an enlarged heat sink in which cooling channels 19 are formed thru which water or other coolant may be circulated.

As above stated an important feature of the invention resides in an eflicient and fast acting means for removing heat from the member 13. To achieve this result a close and continuous contact is established between the outer surface of the member 13 and the wall of the bore 14. This may be done in any suitable manner. A method found to be satisfactory is to machine the bore to a precise dimension and to a smooth finish. The outer surface of quartz cylinder 13 is then finished smoothly and accurately as by a grinding operation to fit snugly in the bore. In this manner a good heat transfer is established between these surfaces. Thus heat generated in the chamber 13 by the discharge occurring therein is conducted to the block which acts as a large area and volume radiation element which may be provided with cooling channels 19 in which cooling fluid may be circulated. The member 13 may be extended completely thru the bore or it may be made only slightly longer than the irises 18 in which case the ends of the bore are closed by the plugs 20.

In addition to the heat dissipating means above described a further very effective means is provided for removing heat from the chamber 13. To do this a separate heat adsorbing means is placed directly in the discharge area within the chamber. An effective means for accomplishing this is to insert a metallic tube 21 into and thru the chamber with its end portions sealed into the end walls of the chamber. A rapid flow of coolant such as water may then be established in the tube which will effectively remove the heat of discharge by direct radiation. Since there is no barrier between the plasma of the discharge and the tube 21 efiicient transfer of heat is realized. Combined conduction and radiation operating in the device of the invention results in a substantial increase in heat dissipating capability compared to existing duplexing equipment. Thus the power handling capacity of the device is greatly increased. The capacity of the duplexer may be increased by a factor of 2 or 3 more.

The tube 21 is made of metal and preferably of a material having the same coeflicient of expansion as the discharge envelope. The tube extends beyond the ends of the block 15 and is connected in a suitable coolant circulating system 22 by flexible tubing 23 or in any other suitable manner.

The discharge assembly consisting of the chamber 13 and tube 21 is readily removed by removing one or both plugs 20 and pushing it out of the bore 14. A new assembly may then be inserted in the bore all of which may be done without disturbing the waveguide system. If the discharge chamber extends completely thru the block 15 it may be readily pushed out of its aperture and replaced with another unit.

What is claimed is:

1. A duplexer comprising a body of heat and electrically conductive material, means for inserting said body transversely in a waveguide, a single wall cylindrical dielectric discharge chamber inserted in and closely fitting in an aperture extending transversely thru said body, a charge of ionizable gas sealed into said chamber, a metal tube extending thru the gas in said chamber and sealed into the wall thereof said tube being adapted for connection to a supply of coolant and a resonant iris in said body communicating from said waveguide to said chamber.

2. A duplexer according to claim 1 and wherein said body is extended beyond the structural boundaries of said waveguide to constitute a large heat sink and means to rapidly cool said body extensions.

3. A duplexer comprising a body of metal having a high heat and electrical conductivity, a cylindrical bore in said body, a cylindrical discharge chamber of dielectric material received in and having close heat conducting contact with substantially the whole area of the Wall of said bore, ionizable gas in said chamber, a metallic cooling tube extending thru the gas in said chamber and sealed into the end walls thereof, said tube having its ends extending to the outside for connection to a source of coolant, means for inserting the duplexer in a waveguide and a resonant iris in said body communicating from said waveguide to said chamber.

4. A duplexer according to claim 3 and wherein said discharge chamber is made of quartz.

5. A microwave switch according to claim 3 and wherein the said body is extended beyond the structural boundary of said waveguide and fluid cooling means acting to cool the said body extensions.

6. In combination with a waveguide system, a duplexer comprising a thin single wall dielectric discharge chamber containing ionizable gas, a flat solid body member of electrical and heat conductive material containing a substantial quantity of said material and which is slightly thicker than said vessel, means to insert said body in said waveguide with its thickness dimension between the ends of adjacent waveguide sections, said body having an aperture therein extending therethru transversely to the lengthwise axis of said waveguide and receiving said discharge chamber therein in close contact with the wall of said aperture, a heat conductive tube extending thru and sealed into the walls of said discharge chamber in direct contact with said gas having its ends extending beyond the waveguide for connection to a supply of coolant and a resonant iris in said body communicating from said waveguide to said discharge chamber.

7. A microwave switch according to claim 6 and wherein said body is extended beyond the structural boundaries of said waveguide and means to rapidly cool said body extensions.

8. A duplexer according to claim 6 and wherein said discharge chamber is made of quartz.

9. A microwave switch according to claim 6 and a coolant circulating system connected to said tube.

References Cited by the Examiner UNITED STATES PATENTS 2,922,124 1/1960 Braden 33313 2,922,131 1/1960 Braden 333l3 2,981,901 4/1961 Reingold et al 33313 2,990,526 6/1961 Shelton 33313 ELI LIEBERMAN, Primary Examiner. 

1. A DUPLEXER COMPRISING A BODY OF HEAT AND ELECTRICALLY CONDUCTIVE MATERIAL, MEANS FOR INSERTING SAID BODY TRANSVERSELY IN A WAVEGUIDE, A SINGLE WALL CYLINDRICAL DIELECTRIC DISCHARGE CHAMBER INSERTED IN AND CLOSELY FITTING IN AN APERTURE EXTENDING TRANSVERSELY THRU SAID BODY, A CHARGE OF IONIZABLE GAS SEALED INTO SAID CHAMBER, A METAL TUBE EXTENDING THRU THE GAS IN SAID CHAMBER AND SEALED INTO THE WALL THEREOF SAID TUBE BEING ADAPTED FOR CONNECTION TO 